1. Field of the Invention
The present invention relates to motion control apparatus and method for an automotive vehicle which are capable of controlling a vehicular motion during a steering maneuver input on front road wheels.
2. Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 10-007010 published on Jan. 13, 1998 (which corresponds to a U.S. Pat. No. 5,957,987 issued on Sep. 28, 1999) exemplifies a previously proposed vehicular motion control apparatus. In the above-identified Japanese Patent Application First Publication, a vehicular yaw rate and so on are controlled during a steering operation (maneuver) so that a vehicular stability during a steering wheel operation is maintained. Specifically, a target yaw rate for a response characteristic related to a plane motion of the vehicle on the basis of the steering angle and the vehicle speed to coincide with a predetermined response characteristic is calculated, a rear road wheel steering angular command value required to make the yaw rate developed on the vehicle coincident with its target value is calculated in accordance with a motion equation based on a vehicular specification value. Rear road wheel actual steering angles are controlled to follow a rear road wheel steering angle command value. Thus, this control results in a yaw motion in accordance with a target yaw rate.
The target yaw rate is calculated by setting a response characteristic of the target yaw rate with respect to a change in the steering angle as a first order or second order transfer function and presetting a vehicle speed dependent constant in accordance with a vehicle speed. Thus, a steering response characteristic of the yaw rate during a low speed run is maintained and a vehicular motion which is superior in a steering response characteristic and stability without giving a sense of incompatibility to a vehicle driver during a high speed run can be achieved.